Aspirator systems are used in a variety of applications, such as automated test apparatus where tests are run on samples of a fluid, such as a blood sample. In such test apparatus, it may be necessary to serially and automatically dispense and/or evacuate test samples, reagents and the like from various containers. During such tests, it is sometimes desired to measure an amount of a sample in a container. An example of such an automated test apparatus are described, for example, in U.S. Pat. No. 6,321,164, entitled “Method and Apparatus for Predicting the Presence of an Abnormal Level of One or More Proteins in the Clotting Cascade.”
Various approaches are known for sensing the presence, level and/or other characteristics of fluids. A variety of principles may be used to measure fluid level and/or other characteristics. One such approach is ultrasonic measurement. Another is using capacitance as used in a capacitance type sensor. Optical sensors may also be used.